Its not an official replacement for the Visual Editor and it depends on what you need it for if it can replace it. If you need multiple resolution support and image rotation, then Visual Editor is probably better.
Visual Editor has a a major flaw, at least to me, anyway. It eats a huge amount of CPU cycles on OS X which is a deal breaker for me. Can't run it on a laptop for long periods of time.
I have completed the Tier 1 code and it is able to display maps created by the scene editor.
Another advantage over Visual Editor is that it only copies the images it uses into the media folder. The bad part is that this requires you to save the project and then export it to AppGameKit, so it adds additional steps.
If the project window looks kinda familiar to Xojo users, its because I based it on an older version of the Xojo IDE.
Still lots of tweaking and bug fixing to do, but its pretty much feature complete for now and is working.
Here's a couple of updated screenshots.